Apparatus for positioning a rotary controlled element



"4 Sheets-Sheet 1 H. F, ELLIQTT APPARATUS ;'F.OR POSITIONING ROTARY .CQNTRQLLED ELEMENTS v .1 ma a INVENTOR. HAROLD F. ELLIOTT ATTORNEY Control Unit llc Q VIIA'IIA'I "VII;

Aug. 8, 1950 H. 'F. ELLIOTT- 5 7,

' APPARATUS FOR POSITIONING ROTARY CONTROLLED ELEMENTS Filed s t. 5,1947 4 Sheets-Sheet 2 FIG.6'

63 (ccw) IN V EN TOR. HAROLD F. ELLIOTT ATTORNEY g- 1950 H. F. ELLIOTT 2,517,854

APPARATUS FOR POSITIONING ROTARY CONTROLLED ELEMENTS 4 Sheets-Sheet 5 Fil ed Sept. 5, 1947 sag FlG.|O FIGJI INVENTOR. HAROLD F. ELLIOTT ATTORNEY 1950 H. F. ELLIOTT. 2,517,854

APPARATUS FOR POSITIONING ROTARY CONTROLLED Emmsms 'Filed Sept. 3, 1947 4.,Sl18ets-Sheet 4 l 'l I v f 5; FlG.l2"

I I H 7| r 3 224 64(cw 77 g 5 v 5 E A v Potenfiul Source INVEN TOR. HAROLD F. ELLIOTT ATTORNEY patented, Aug. 8,

APPARATUSF0K PDSITI0NiNG' A R0TARY' CONTROLLED ELEMENT I a namnnmntw; rmmtotcnirz'; lrppiicatien-sepwmber 3, lilli'ig ser-ial-Ndfl1 2300 Theapresent .inventiomirelatestcimzgeneral, t0 apparatus forprecisely-positioninga'irotarygcone. trolledrelementiinz-avpredeterminediangularxposie tion-i v The-apparatus shere'zpropose'dizis subiectdo awwlide:rangemfiapplications andnma ad-yane tageouslzy; employed in-lconneotiomwith :anyl elee trical onmechaniaal systemshaving :va ontizolled element atoirbeppsitioneduin anys'one-eofis'everai preselected settings. For example, in.atheefields ofqradi wada-r, ltelevisiom'andrfacsimilexitiis (pustomary; to determine: 1am operatingeaconditionioi the apparatusnthroug-nzthe' useeofasttuning :elee ment'whichcvmayi beise-lectively addiistedii Eon convenience,- theninvention:rwillllbe:r descrioediain' detail,'iinxconnectionwwith the selective tuningiof a wav'eesignalreceivers v V A ,Controhapparatus. zfor4 -=accomplishings;a "desired tuning addustment of; ac-radioz receiyern have readynbeerr proposediand: frequently embodmsa series, or; selector? camsmotatableeoveri ail-range slig-htlyiless .than 180 Eachv camincludesiaistop device,=,such aasi-z ar-zreeessw andrhasi an i associated cam-follower-provided with moo-operating stop device, usually inthanaturet otgaaprojectingjelen merit,ntofregister,:with1thestop .reeess and arrest rotation of the cam s eries; I The! {controlled ie lee ment? is directly coupledtwithe asrotatableeshaft upom whichzthek series-oi cams z-isizsecured fin :ad'e justably -fixedl positions, zandeselectorr magnetseor thelike when selectivelyr energized}- arrestathe controlled elementin ,a preseleoted ,positionatdee termined by the particular; camand ifoliowemaee tuated by theselectedmagneta. Arrangementssof this ,type alsoe-haveanreversible' driving;,,system controlled by asensing device-1130 driverany see leeted cam 'toI its-J home, position throu he the shortest langulandistance i While such apparatus has .been used, it is found. thatgtheresmay beesome inaccuracy due-to play innthe driving systemeif the selector cams-:ane permittedto berzarrestedzin home: positiomfrom either-(direction 50f: notation? In-.- United StatesslietterssPatent;Noel2;299,(18B; grantediapplicant iOctober zo 1942 19116.: entitled .Electric ;Contro1-- Apparatus?! there .descnibed and: claimed aacontrol vapparatusrzof the:foizegoing type; but having ,a s pivoted interloekaelement ton thee cam follower; the interlocks: beinggsbiased-xto cause; the step projection normally; towbe too large 'to' register with rth'esrecess ofa'v its -:;selector cam.- The sensing"device twhich'zreverses the-di rection. of rotation.=. aihyif'timez fth'e cams drives througlrits *homespos'ition mithout reg-istrationizof thee stop; devices;;Vcontrols gtheesysteimtorpermit such registration only as th'eecam xseleotor homes iromrza .zparticularrdinectiom .Thmpresentfinfln- 1s blainisa (on-14:1 :21

ti'onsiss: directed-i too air control apparatus: of ithe typeedescribed including: a; siin'plifiedi interlock mec-l'ianismn. v

. Anothericontml'sazpparatus ftmwhicltthnsinvens tion is especially:adapted;l formsetl ieiasu-biiect1ofv applicant s y'concurrently. *filed' application: Serial No:-' '7'l'1 ;999, filedi September 3; 1947, and'ientitled Apparatus;-fonr:BositioningtsaeRotaryz Controlled Elemen .1 Thee-apparatusiof" that? application is ointhe mutt-revolution: typeeincludingrfla :seriessof. units individuallyrcomprisingia;iastcmiemberzroe tatableewithinnvmulti-revolution:range andalhav ingiston; provisions: foniregistering awith': a; stop device to; lp0sitibhfith'w COIltIIOHBdCiGlIIlBIItL The stem device: is itnorm'allyr in; i an. inactive-2 position audazwslow mem'beracon'currently drivenlwitlt the fast member ShiftSDtheiiStOp deViCGy:tOilitSffiCtiVB position whenfthe slow member'ireaohes "zazgiven angularr setting-5. l East operationaisr achieved by a sensingsdevice:awhichmontrolsrthetdinectionvof-iro 'tationntoeeffectadirectIhoming of the slow mem a fiirther objecti'oi the invention to prm improvedand simplifid'sequen'cecontrol fonf'apparatusifor positiorringaa-urotary con-trolled elementiimaipresel'ected angularsspositi'on It istasspecifiozobj'ect of theeinventionx to pro= vide anrimprovedsequencecontrolimechanism for controlic apparatusz of fthei' nmlti-revolutiono type utilized: for positioning-m rotary controlled-isle; mentifinta ipreselectediangular 'position; x

Ima'ccordance withvthe inventiomapparatus for nosition-inggas rota'rmcontrolled ielementsimai spree selected angularipositioncomprises a stop :d-evice forrcontrollingstheipositiomof the cont'rolldzelee mente Theaapparatus includes ai'rotatable mem b93312 having-'1 provisions for registering:v with: the stopidevice' on'ly when that: member is .in :a re; determined-t: angular" position; The rotatable member has at least a portiomwhichds:displaces able :to .simulaterrotationioflcthat'imember intone portion of the rotatable member when that member is initially in its predetermined angular posi-" tion to cause the sensing means to establish an opposite direction of rotation. For a better understanding of thepresent invention, together with other and further objects drawings, and its scope will be pointed out inthe Y appended claims.

Inthe drawings, Fig. 1 is a view, partly sche' matic and partly in cross section, of an apparatus embodying the invention in one form; Fig. 2 is an elevation view of the apparatus of Fig; 1 partially broken away to reveal certain of the mechanical components; Figs. 3'and 4' are detail views of the apparatus of Fig. 1, and Figs. 5, 6, and 7 are schematic representations utilized in explaining the operation of the Fig. 1 embodiment. Figs. 8 and 9 are schematic views representing a modification of the invention, and Figs. 10 and 11 represent a further modification there of. Fig; 12 is a fragmentary view in cross section of a control apparatus embodying the invention in still another modified'form; Figi 13 is an elevation view, partly broken away, of. the are rangement of Fig. 12, and Fig.14is a-detail view of a portion of the apparatus. of Fig. 2. ;.Fig.- 15 is a schematic representation Of. a control.rcircuit which may be utilized in lconnection. with any of the modified forms of the invention:

Although the invention is subject to a variety of applications, it is especially useful in providing a sequence control for apparatus of themultirevolution type utilized to position a rotary-controlled element ina preselected angular, position and will be described in that connection. By the expression multi-revolution type. is: meant apparatus including a rotaryv driving element effective to position a rotary ,controlled element in any selectedone of a plurality of predetermined positions, any two of which-may have, an angular separation represented by rotation of the driving. element exceeding onercomplete revolution. -1. 1

Referring now more particularly to Figs.;-1 to 4, inclusive, there is represented apparatus-of the multi-revolution type for precisely positioning a rotary controlled element in azpreselected one of a series of predetermined angular positions within its rotational range and including the present invention in one form. Whilethe apparatus is to be described in connection with'determining the tuning adjustments of a .radio receiver, the receiving system, per se, forms no part of the invention and, therefore,- onlyfits tunable element I'll has beenaindicated in order to'simplify the drawings. Element I0 will be considered i as the usual adjustabley'condenser which determines the operating frequency of the receiver although, as is Well understood, sev eral such condensers or equivalent tuning de-v vices may be ganged for simultaneous or .uni control adjustment.

In .orderto realize a selective control of the rotary controlled tuning element H] as between several available predetermined settings, the apparatus comprises a plurality of control units which are mutually oriented so that each corresponds with an assigned one of the desired tuning settings. The control units are designated Ilal I ,f, inclusive, in Fig. 1, but since all are of substantially the same construction, only the firstilftwo have been shown in section and the re- 'm'ainde'r are indicated schematically by dashdot blocks. "simplifies reading of the drawing, shows the structural arrangement of two control units and "common" or interconnected portions thereof. ,Each of these control units is adjustably fixed to "an'enlarged'section ll of a shaft [2 which is 3: --rotatableover arange of many revolutions.

The method of illustration chosen A gear train l3, l4 connects shaft 12 with tuning element In, a suitable speed reduction being employed so that rotation of shaft l2 throughout its entire'range effects only the desired total displacement ofthecondenser shaft, usually of theordef of degre'es. By virtue of the connection'of shaft 12 with the tuningelement, each preselected angular position of the shaft determines and corresponds with a related tuning position of'the condenser shaft and a selected operating frequencywof the receiver including this condensers v '-In describing the construction of the control units," 'rference will be made to the first such unit l tla,.but it will be understood that the descriptionla'p'pliesequally well to each of the remaining ones. Control unit I la comprises a fast rotatable member 200. adjustably secured, in a manner to be described hereinafter, to shaft section- I 2' for concurrent rotation therewith. Member -20ais, therefore, rotatable within a multirevolution range and is provided 'on its external periphery-with'stop provisions which may take the form of a recess Zla clearly shown in Figs. 2 and 5. [The control unit also includes a stop device for controlling the position of the rotary controlled element by engaging with the recess 2 la 'of fastmember 20a. This stop device is movable from n inactive position into an active position wherein it is able'to engage recess Zia of the fast member and" is shown as a bell crank 22a. pivotally supported upon a shaft or rod 23 which is common toall control units. One arm of bell crank 22a is provided with a projection 24a proportioned to be received by recess 2 la. The projection 24a is maintained in its inactive position by mean's'er a. leaf spring 25a, anchored to the frame of the apparatus and engaging another projection 26a of bell crank 22a normally to rotate the bell crank ina clockwise direction.

The engagement ofstop projection 24a with fast member20a, when unit Ila is selected to determine the position of controlled element In, is un er; the control of-a slow rotatable member 21a supported in'substantially concentric relationwith fast member 20a and permitting engagement of stop element24a with fast member 2Bdonly when the slow member is rotated to a predetermined angular position. The slow memberZTa; has the' form of a cam ring and its average diameter exceeds that of fast member 200.. It has a low cam portion 280. and a high cam portion 29a,'where low and high indicate the order of cam radius. Each cam section subtends an-xarc of-wslightly less than 180 degrees and a stop recessiiwwon the-external periphery separates the cam sectors.

lit-least a portion of slow member'zlc is dis! ear:

b blaceableitosi-mulaterotation ofithat memberiin one direction, specifically aclocliwise direction, over" a small fraction-= of -arevolution the case under consideration; only aportiomof tlie rota-table member is displaeeable andi tha-t por= ti'oncompriseszan -.interlock plate 3'! a, of? ar'cuate configuration shown in"FigS; 3"'-and" 4. The plat 3m is:-:slida;bly supported' on theslow rotatable membersim the vicinity of? its: recess" 3012;. and? whendisplaced; at least partiarlly fills thati res CBSSi Morezspecifically; shoulder studs flwe 33a; whichenterr elongated slots of platec31 a; slidably snpport'ithatsplate on'ithe highlcam portionflllh:

soothat. displacementtor:thesplate. effectivelwcons stitutesrian "extension":ofitlinieh'ih cam ise'ct'or a Theiapparatussfurther rincludeszsaadrivingz sys; temiforasimultaneously wdi'ixzringzthesfast hands slow members.satianpreselected speed ratio;.. Theadiiwingssystem-rcomprises.zaehypocycloidal:planetary gearr-systennpositionedibetween these rotatable members .in.-coaxial;alignment therewith and'iine terconnecting them so that rotation of one effects simultaneous rotation. of;thesiotl'rer-rv at theadestredcspeedaratio... The:,=hypocycloidal-;geamtrain is-;provided:: by a ipinionior: sunigeareall act-received and rotatable-z within. at well. orz'recess .in a: hub member. Hai -mechanically, secured .tosfastimeme ber Mammshowntinfligs. .1 and-2:. Sun gear: 34a is: freely rotatablei on .aistud.shaft.affixeduto;v fast member 29a and is in constant: meshing. engagee ment with a rotatable gear. fib-a-iormed onthedm ternal periphery oi. the: ring-dike. slow member 21a. and an. internal .gear. 3:lalproyidediin. a star.- tionarymember'taa. Memberi38a; as represented in Fig. 2,,,has..a-. bifurcated portion; 39a. which receives a rod 40 for.holding that member and its internallgearrfld..stationary. Roddlhis-common tccalllof the. control-units. I

Therdiameter. of. hub memberv 35a is;selected.ito be..only slightly; smaller than that of gears 1 36a; 3.16, sothat the huhmay. serveas. a bearingsup, port for. such gearsrwhile attthe same. timebeing rotatable relative thereto. An .end' plate-Ala, Having a diameter exceedinggthat lot-.hubpmems ber 35iz, serVesaS a stop, collar to maintaindgears 3Ba.and'315t Onthe/hubl. Rivets 4221, 4211 1001;

fast member 20a, hub 3511 andiend platefl la. into one mechanicalassembly... In order: to .introduce .a desired? speed differential;.. rotatable gear 362; has more teeththan stationary gear. 3Ta. Where .the. eii'ective rotational.rangeoflshait. i2 is" to'be thirty revolutions, gear 36...may. have siXtyrfiv'e teeth andlgear 31d. may havesixtyefour teeth. The driving systemis completedlby means for. rotating. shaft I 2"andewitli itffast'member2 a. This means is providd'byl alreversiblemotonfl,

connected" through a conventionallslip. clutchAl' and a: gear train 45. 48; inclusive, .tdshaftLl 2. While any of a. number oil'knownmorinecting arrangements maybe employedto securethe iast member assembly 20ar35al Ia ,to shaft section I2; theone' shown. includes.- a. hub. 55?; suitably attachbd t'otheshaft," as .byfa' press fi'tL. The hub has'a. shoulder. 56:; atlone end up on,.which.mem= b er 2'01: maybe rotated." Awasher 51'a,.,in .cone junction withia clamping.v screw '8a..-locks thee-fast rotatable member ,2llal'toitsi i-ub. in a preselected angularposition and constitutes means-for.pro..-v viding a continuous .driving connectioniromsone of thee rotatable...members, specifically from. the fast member, to. the. rotarycon-trolled .-tunin%:ele ment IILthrough.shaft-lll.

, An. extension waoiwbell crankifia serveseas the armature of: an associated;selectonfmagnet' 6121.

which maylbe energizedi tor.selecticontrolmnit l It toi establish itsrzassignedisettingg or'i condensers i througmslrraftoll. r

Therinventionw contemplates adirectiinomingiof tlieefastandii slow members? to? their tpredeter-ss ntinedizpositions that 11s,: a control 3: or: thezdirece tron: or rotation:.-which results im driving 1 such members; to; their: home: positions. through the sliortestepossiblei. angular "distances. This: is .ac1-1- complished Ebyzazsensingzmeansg: responsive; to: the orientationmf: slow member: 2:10; relatives to. its predeterminedsor: home position,..for' control-ling theedii'ection.1of:;rotation .of 1 the. driving system: The sensingrmeans comprises'ia'switch of thertwoe pcsitiomtyne havingi'a .movablecintermediate.ree

silientrcontactrfiiq which, may engage either. of

opposed,fiiredscontaetstfiiiafifl.:. It willibleuassumed that-.the;motor=circuit completed through contact 63, as described hereinafter, establishesrascoum terrelockwisefrcew) 'directionxof rotationrforlthe planetary-gear; system-v and rotatablenmembers Zflwand.2 lwaw'hile-contact .64 establishes .anoppo'e- Si-l36a0F5C1GCkrWiSB(CW) direction. of :rotation: The n agement: of movable contact .fi-2zwithzits; asso+ ciatedfixedzcontactg; B3 :andfil is..determined:;.by atswitch actuating..- device in the. form of arbiail 6 5 iextending gover a further extension GGauof. bell crank; 2 2a.:to..:be-:-engaged thereby and: actuated in accordance withthe orientation ofyslow-imember 2111, 4. Theibailfii similarlyext'ends over; the coraresponding projections :of: the-bell cranksuin each of the remainingcontrol units:sothatanwonesee lectecl'lto' control-the apparatus may accomplish directehoming Normally, contact 62; is closed schematically indicated at E5:

upomcontact. 63 andisoretained there: forrsmall throwseo f .bell..crank 22av and bail. 65;. as. shown in Fig 1. 5 However, greater. throws of 3 the bell crankishiftcontact BZ'into. engagement .with'acon-itactGGQ-aeindicated in'Fig. 6. ,1 i

The apparatus further includes means for dise placing thedisplaceable portion 3.Iaof slow member 21aawhen-the slow member is initially inits predeterminedsor;homeposition to. avoid a possiblevmode ofloperation to be discussed hereinafter; .While this displacement may be accomplished. if desired,- only when .the:-s10wmemberziss initially in its.home-position,= itris convenient to employ the. springflflm shown. in Fig. 3, for normally and 'yieldably displacingthe. plate 3m The-spring is..,anchored .atroneaend to stud 33a. and atrthe other." end-tota projection on plate 31a: Itineramally; positions the plate partiallyto fillxrecess 30a. of theslow member, as representedwin Fig: 6".

A-"su'itable circuit arrangement for energizing motorrflsandg theeselector magnets 6| is represented. in. Fig; 15, where the .potential source :is The. customary pushi-button controls 162. are provided, one for each control-unit. The'spushbuttona closes contactswl'la and: 18a:to complete the motor circuit and;alsozcloses'acircuit at the contact 19a forrenergizing a selector magnet 6 la. The switch 62'-64 is shown: connected {with a split field-wind irrg: for: motor 43; providing reversible control ofiith'e motor operation. The interconnection of bell-:1 crank 22av with the movable contact 62 representedschematically at- 8 l As previously pointed out, the several control unitsrare-idntical inconstruction and the ele-- ments' thus far recited" having the designation character a are duplicated in each of theotlrers. It will benoted in Fig. 1; h0WEVEl,l;h'2tfi the clampingserew-fiw of unit lib passesthrough the hub 55b; of the=preceding unit. In similar mannerytlie clamping screw for any other unit .ft'zrtlieri'aionge the -stack or serie's' passesi througg the hubs of the preceding ones and is accessible for adjustment at the front of the stack.

. In utilizing the described .apparatusto position shaft l2 and with it the, controlled tuning condenser l into any of the several possible preselectedpositions, it will be understood that-the fast and slow rotatable membersof each .control unit are. initially oriented relative to the shaft to correspond with an assigned one of the selectable positions. achieved by first pressing a selected push button, as 16a, and holding it until home. position is reached. The corresponding clamping screw, as 58a, is then released, and shaft [2 is rotated by knob 82, until the desired settin of condenser is reached. The clamping screw 58a, is then retightened and the operation is repeated for the other positions.

Having oriented each of the-severalcontrol units in the manner described to correspond with the-selectable positions of controlled condenser In, the apparatus may thereafter be employed quickly and precisely to position the condenser into any selected one of its available settings. Alternatively, a knob 82 coupled to shaft 12 enables an operator to tune the receiving apparatus independently of the control units and to tuning conditions other than those assigned to the control units. The remainder of this description, however, will be devoted to tuning operations through the aid of the several control units.

With the apparatus at rest, springs urge all stop projections 24 away from their associated slow members 2? and bias such stop projections to their inactive positions. Where the apparatus is to position the tuning condenser, the push button Hi for a particular control unit is depressed, completing the energizing circuit for motor 43 and the appropriate selector magnet.-

Assuming push button 56a to be actuated, the motor circuit is completed and magnet Bla is energized. It attracts its armature 60a and rotates bell crank 22a in a counterclockwise direction about its pivot 23, causing stop projection 26a to be brought into engagement with slow member 27a as a cam follower. Depending upon the position of shaft H2 at the time'th'e selector magnet is'energized, stop projection 2 m will usually engage either the high cam sector 29a of slow member 27a, in a manner similar to that represented in Fig. 5, or it will meet the low cam sector 28a as indicated in Fig. 6.

If the follower 2 3a engages high cam portion 29a, there is a limited or restricted resulting rotation of bell crank 22a so that middle contact switch 62 remains in engagement with contact 63, establishing a direction of rotation which is counter-clockwise, as viewed in Fig. 5. With motor 43 energized and the planetary reduction gear system interconnecting the fast and slow members, these members rotate concurrently at ,a preselected speed ratio, 65:1 for the described planetary system, until slow member 21a not only arrives at, but is driven beyond, its preselected 91' home position. The slow member is driven past its home position because spring 'Hla has displaced interlock plate apartially to fill the recess 30a of the slow member, providing an effective recess which is too small to receive pro jection 24a.

This direction of rotation continues until interlock plate Sic is also driven beyond stop projection 2%. At that time the bell crank 22a moves into engagement with the low ,cam portion 39a. .Tbis added displacement of the-bell. crank This orientation may be shifts contact '62; to contact 54,- reversing the direction of rotation of the driving system. This condition prevails until stop projection 24a engages the leading edge of interlock plate 3la and, by overcoming its bias spring Ma, pushes the interlockplate in the direction of high-cam section 29a of the slow member. When the interlock plate has thus been removed from stop recess 30a, stOD. projection 24a is received by that recess. At that time stop projection 24a engages fast member 2ila as a cam follower and, when recess 2la is also brought into registration with stop pro jection 24a, asshown in Fig. 2, the entire driving system is locked against further rotation. This locking is effected when rotatable members 20a and-27a have positioned the rotor of condenser I0 through shaft 12 to a preselected point in its rotational range and is permitted by virtue of. slip clutch 44, which is arranged so that motor spins to a stalled condition when the rotatable'member becomes locked at home position.

'When the initial orientation of shaft l2 and slow member 21a is such that low cam portion 28a:is. opposite stop projection 24a, as represented in Fig. 6, the first movement of bell crank 22a is sufficient to break the motor circuit at contacts 62, 63 and complete itthrough contacts 63, 64, initiating a clockwise sense of rotation. The driving system then actuates the control unit until stop projection 24a displaces interlock plate am from recess 38a of the slow member, permitting the stop projection to register with the stop recesses in both the slow and fast members to arrest the shaft and the controlled tuning condenser in its selected position.

- The movement of any bell crank 22 upon the energization of its associated selector magnet performs, in conjunction with cam portions 28,

29 of the slow member and switch 62-454, a sensing' function to determine the appropriate direction of rotation for direct homing. The expression direct homing is used herein and in the appended claimsv to indicate a direction of rotation which drives the controlled element to its preselected position through the shortest possible angular distance.

While the operation as described may be relied upon for many operating'conditions, the interlock plate am provides an interlock or sequence controlwhich avoids one possible mode of operation that may, under certain circumstances, result in jamming and inaccurate tuning. When tuning between two stations that are very close to one another in the freq'encuy spectrum it is possible to have an initial condition such as represented-in Fig. '7 because each fast member is driven any timeshaft l2 rotates, and each slow member necessarily follows the rotation of its fast member; Here the expression initial condition indicates the setting of the controlled element immediately prior to the actuation of any selector magnet'to achieve motor-driven adjustment of tuning condenser I0 to 'a selected predetermined position, In Fig. 7 the apparatus isshown without interlock plate 3m, and slow member Zla is at itshome position while recess 2m of the fast member is on the clockwise side of stop" projection 25c. In the absence of the interlock plate, stop projection 24a, is free to register with recess 30a of the slow member upon the energization of selector magnet Bla. Were that to be permitted, projection 66a of hell crank 22a would close contacts 62 and 64 and establish .a-clockwisedirection of rotation. carrying recess slow. memberIZ T through pinion gear' t member" I38 while.. at'thesame time,

2| a.,-,-away 'fromestop. projection .24a'1and bring: ingthe .trailing :edgemtrecessifla against the stop projection, resulting in Jamming and terroneoustuning.

Jamming isavoided.byinterlockrp1ate..3 l,a and its spring ma which displaces theinterlock plate partially to fill..re.cess .sfiapas cl early.shown in Fig. '6. As. a consequence, .when. the .initialcondn tions-rof Fig. .7 .would.otherfwise..exist, the, interlock plate effectively extends .highecam sector 29a. of .the .slow member. This .is .eduivalent t .or. simulates rotation ,of. slow.member 2'la,a= small fraction of a. revolution in..a clockwise. direction so that when/magnet filo. is energized .thecon- 'ditions representedjin .Eig. $5.,arise. .As-airesult,

the-apparatus .follows the.firstedescribedseguence of operations in which .the .rotatableunenibers are driven in .a counter-.clockwise -fciireetion',to move recess 2 la. 'to1the. counter-clockwise .side of projection] la before the @direction of. rotation .is reversed. In thismannerthecontrol uni-t properly, positions the .controlledytuning .Qcondenser li) xandipreclu'des any possibility ofjjamming'. Thus, it is apparent that the interlock plate causeslthe .fast-and slow members to.arriv.e at their home positions from" the same direction irrespective of the initial conditions. "'Thistakes up all slack andlost motion in aggiven iiirectionfforalltuning operations and assureshigh precision'in addition to preventing an erroneous :operating' se- -quenc.e.which otherwise causes jamming. A

.While 'it is,pre'ferable.to displaceonly a portion of (the "slow rotatable member to effect. a sequence "control, 'as explained in conmection with the embodimentoi Figs.1-f%,'inclusive,f the "but it .w'illlbe understood 'thatthenumber of ,con-

trol .units employed, whatever "form of .the invention' they embody. is determined by the number of .preseti positions Idesirecl for the rotary econtrolle'd .element, i tuning .condenser I m. T

.In' the. arrangement represente'dlin' FigsJ S fanid 5 9,. slow rotatable member 1'2? is JidisplaQea-ble" over a smalllfraction of ,a .revolution'in ,a "clockwise ..directionlindependently of the driving system. in-

cluding motori4'3. "Tothat end-.the' bifurcation .139 of stationary member I3B.is.seleoteidftoflbe larger than'Tthef'diameter of rodM anjcl'an additional .springZB5,.a,nchored. atone, end toftheapparatus "frame and bearing against bifurcation 39. .tithe other, normally Tdisplaces stationary membe -7I3B a small portiomofla. revolutionima clockwise "direction, as ;viewed' in"F ig ."9. ;.Since the internaLgearjl offstati'onary memberfftilris continuously connected to internal gear. {3550f heiretatable .member 'displaceable with ary bein'g ro a tablerelative'thereto. v 1111 '.\the operation l of Lthis embodiment .iof I Tithe invention. .springlS 5..displaces f.the normally .sta- 'tionary member [38,and, witl'kitsrotatablenmember 21 prior to the energizati'on of motor l il. When .motor 43. and magne -Bl .are energized,

, .br-ingingrtstop .projectionJMagainSt slowrmember .12] as. a cam .tollowermans.initial direetioryrofiretation..,is establishedmo effect direct homing .of slow ..member .21 and ,iast :member 20, .as .previously. explained. therotatablamembers are driven, stop projection e24 .registers vwithtstop recessesuau and. 21 in turn, always. engaging th latter when the driving-system c-is. rotating-fin va clockwise.direction as represented-in .Eig fi. the ,horne positions are gapproached, proiection .24 abuts against one edge {Of {recess .30 .in the slow. member; and. displaces :both .this..slo w.mem- .ber and-stationary member I38 {infra countenclockwise .dire,ction-1hy. overcoming the ?force of spring-:8 5. .The finalhome position.is-.-shown in i -+8..

If-, .heglectinethe: eIfect-oispring 58.5, momentarily, the -.initial position .of .the .slow @member is -as .depicted .in Fig. ,7 with recess .3flasadjacent .StQPvPI-VQJeCtiOn,-24;\th displacement ointationary member I33 and slow member .zlsundertherinfluenceeofvspring ereates.-.a conditionsimilar to .thatlrepresented in.Fig.;-9.- .Energization ofanagdiet-n6 i then bringspr JectiOm Zl-i-nto en a ement with. liighcamesectonz 9 .so thatthe. initial-direction. .of rotation is counter-,clockwise,c ermittin .recessl2 I of fiast. member .2 0 .to .be positioned to the: counter=clockwise sidelof-proj action .214; before the direetionpf.rotationisreversed. .lnithislway, spring 18.5 .by displacing members 21 and $348 accomplishes .,a jdesired.,.sequence control. LRo'd 41M limitsthe dis olacement.ofvrnember I38 iniboth .directions. so .,that.accur.acy.. in setting the: rotary controlled ielement iconneeted to .shaft 42 eis inherent, v

' I .The modification .of .Figs. 10 and..1 1 .is similar inmanwrespeets torthat. of.Figs.BendQbutrelies n spri g l inein.thamen v. earlsystemt displace .slow member 4.21 .for +511IQI1C6 scontrol. .A-supplementarypinion 8E6 is provided; beingrcar- ..ried:byrandifreely rotatablaupon astud shaftgfll isecured tmone. end 01:3 lever 8s pivotallahoutna r-pivot; rod..&9. To 1 obtain .a .lcompact. structure, it is. convenientto. havenpivot rod ,8.&, extend .between ,fast .member .4 20 and the; loekingsdisc A 1 shown .inFig. 1,..to rotate therewith. ,A cutout oryvindov v is provided in fast member I20 and lever .88 i ispshaped to rest rinathe planeeoftthe .window. ,A ,spring 8 I .ho1ds.pini0,n.8$ in.; .eng;agement.with rinternal gear 36 .of.:s1o.w .m-emberi L .anddnternal gear-.31"ofsstationary,member.-38. JIheaction :of springcdl takes up .the .-slack-,between.ltheegear --.teeth-and constitutes meansfor displacing. rotatablemember .2l-,overi.apsmall fraction ot-a. revo- ..Lution. With the arrangement.- represented; slow member .2 1 .is displaced,. ,-i-n a. clockwise; direction. ,Eor .an :initial (condition -.-which, without -.the benefit of the sequence control featurerisiasindb i called in-Fig. 31,; spring-.9 I .displaces.-.slow. member .21 .to .=estab1ish..the relative ,:orientation of .this .member .and .stop projectionfitshown in Eig., .11.

dfl helsequence centroids.thusseemtobe .verysimi- 1ar to that achieved {with the ..-arrangements.:of Eigs. 8.-.and-9. As ."rotatableqmembersl- [202331111121 Mar-rive at home position land proj ection .24 .reg-is- .z-tersv with recesses Z hand. 30,5111]: thermannerrepresented in Fig. 10, springs!)hpermits'pivotleversw and pinion 86 to be lifted:soi l hatsslowimember -21 may .shift slightly :a-in ya QCOUIItGF-zOlOCkWi-Se direction. This ;oauses;;-recesses 2| land @3010 :become; more fully-.alignedwandr. enables proj ection .241fully.toeregister therewith.

vAnother springiloadingearrangement;-iszrepresented ,in Figs. 12-14, -ine1usive, wherein ithe 2 planetary ear .system.comprisessa; spur gear. [.36 connected .to. slowimember .I.21 .and. a .-spur;.gear l 31' {,QQPnQGt d i tor-stationary member .138. Ih

spur gears have unequal numbers of teeth, as explained in discussing the first embodiment of the invention, and are engaged, respectively, by similar pinion gears I34 and 234. The pinion gears are supported by a shaft 93 which, itself, is supported by and rotatable within fast member I29. Gear 134 is rigidly aflixed to one end of shaft 93 which has a flattened portion at its opposite end received within an aperture 94 in the hub section of gear 234, as illustrated in Fig. 14. Aperture 94 has straight sections which are spaced slightly greater than the distance between the flattened sides of shaft 93 so that thereis limited play of the shaft within the aperture. A coiled spring 95, anchored between shaft 93 and gear 234, completes the interconnection of pinions I34 and 234 and provides means for eifecting relative rotation therebetween to displace slow member 21 for sequence control.

The spring 95 causes shaft 93 to be displaced within the limits established by the relative dimensions of the flattened portion of the shaft and the aperture 94 in gear 234. Accordingly, gear I34 is displaced and shifts slow member 2'! a small fraction of a revolution in a clockwise direction. Hence, when the conditions of Fig. '7 would otherwise be encountered in tunin between two stations having closely spaced frequencies, this displacement of slow member 1, which is in a clockwise direction, gives rise to the relative arrangement of parts represented in Fig. 14. Therefore, the initial direction of rotation is counter-clockwise, assuring that recess 2| offast member I29 is to the counter-clockwise side of projection 24 before the direction of rotation is reversed. As the home positions are approached, the lost motion introduced by the play of shaft 93 within aperture 94 permits slow member 27 to be displaced in a counter-clockwise direction, against the action of spring 95, so that recesses 2| and 39 become fully aligned with one another and completely registered with projection 24, as shown in Fig. 13. This modification is seen, then, to be similar to that of Figs. and 11.

In each described embodiment, the invention is used to establish a desired sequence control in apparatus of the multi-revolution type, although the invention, especially in the form of Figs. l-4,

'inclusive, may also be employed in apparatus wherein the rotational range of the controlling elements is less than one complete revolution. All forms provide a mechanically simple sequence control for assuring proper operation and for avoiding any tendency toward jamming or erroneous tuning.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a stop device for controlling the posilate rotation of said member in one direction over a small fraction of a revolution; a reversible driving system for said element and said member; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to eifect direct homing of said member to said predetermined position; and means for displacing said displaceable means when said member is initially in said predetermined position to cause said sensing means to establish an opposite direction of rotation.

2. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a stop device for controlling the position of said element; a rotatable member having pro- Visions for registering with said stop device only when said member is in a predetermined angular position; means comprising at least a portion of said member and displaceable to simulate rotation of said member in one direction over a small fraction of a revolution; a reversible driving system for said element and said member; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to effect direct homing of said member to said predetermined position; and yieldable means for normally displacing said displaceable means to cause said sensing means to establish an opposite direction of rotation when said member is initially in said predetermined position.

3. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when said member is in a predetermined angular position; means comprising at least a portion of said member and displaceable to simulate rotation of said member in one direction over a small fraction of a revolution; a reversible driving system for said element and said member; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to efi'ect direct homing of said member to said predetermined position; and a spring normally displacing said displaceable means to cause said sensing means to establish an opposite direction of rotation when said member is initially in said predetermined position.

4. Apparatus for positioning a rotary controlled element in a preselected angular position cornprising: a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when said member is in a predetermined angular position and having an arcuate portion displaceable along the periphery of said member to simulate rotation of said member in one direction over a small fraction Of a revolution; a reversible driving system for said element and said member; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to effect direct homing of said member to said predetermined position; and means for displacing said portion of said member when said member is initially in said predetermined position to cause said sensing means to establish an opposite direction of rotation.

5. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a stop device for controlling the positionwf:saidzelement5-a:rotatabletmemberiliaving sa peripheralastomrecess for registeringtwith said stop? device when saidrmember is inza :predeter :mined zanguiarz zposition and'ohavingza; portion which is displaceablea atxleast;partiallwtofillesaid reces'srand.ipermit'iregi'strationoofasaidzzstopide- Vice and recess only when saidmemb'er riszno- -tatedxtozsaid :predeterrnined-zpositionffronr.aaparr:ticular direction; 2 arreversible drivingh'zsystemfrfor esaidzelementcandz:saidnmember; sensingzmeans,

responsivertoitheu'orientation'of sarid membenrel- :ative to said predetermined position,=c.cfor*cconetrolling:itherdirectionrof:rotationcof said system ;to-=xeffectadirectJhoming: 10f ssaid: member tossaid zpredeterminedi'position;:andtmeems torrdisplacsat rleast,;ipartiall-y= to; fillrsaid recessaanjd permit registration of: said .-stop-. desx,ice -.zand recess-o ly when said i memberz risi-vrotated Ai esaid-g'predetermined ,position from aparticular direction a reversible driving wsystemor ssaid aelement, :and N said memberwsensing, means, responsive-to the oorientationaof said-: member .r'elativato saidpredetermined ;,position, for controlling the direction of v rotation-of said-system toheffect Tdirect homing ..of i :said ememberato 7 said predetermined r.positionuandyieldable-imeans foridisplacing said ,interloek plate when .saidmember is initially in .c said predetermined positionto cause rsaidssensring s means to sestablishl .-a sdirection of (rotation oppositetosaidparticularsdirection.

"7. Apparatus for positioning a rota1,=y ..con- =trolled element ina preselected angulariposition comprising zq-aistop (device. for controlling the, po- .stti-on ofa saidaelement 4a .rotatablevcamimember having high: and lowscam sectorsiindividuallyless than lsosdegrees separated by" ':a speripheral top 7:

.. recess for receivingsaid stopzdevi-ce ,w-hemsaid 7 member: is in a 1predeterminedran ular osition an: interlock, \plate of aarcuate sconfigurationwslid- .ab1yv supported.onsaid-memberin the 'vicinitywof said recessandrdisplaceable a1ongithe periphery .ofsaid members-at least-ipartiallyrtofillsaid -recess and permit l registration-of SQ/id stops devicewand recess onlywhen; said memberis-rotatedtosaid predetermined position from asparticularzdirection ;-a reversible :dri'vi-ng-systemriorr saidielement v and i said imembemsensing .means responsive to the l orientation ofisaid member relative tosaid predetermined position, for -controlling the:d-i-

, rection oflrotationvotlsaidsystemvt efiect direct homing on. said mem'ber to.-;said ;;predetermined position; and yieldabletmeans ior displacingsaid interlock r latewwhen said g member ,initially in said predeterminedipositiomto causesaid-sensing meansto establisma directions-oi rot ation oppo- 70 a connected wwith= :said stationary; member for .dis-

site .tosaid particular direction. I M

\;8...Apparatus for r-positioning a rotary acentrclled lelement-in a preselectedrangular positien comprising :lia .stopgdevicerforncontrolling the;- position; ofr-saidrelement rotatable cam member JesScthansmordegrees.separated:by-sa peripheml stoparecessrfor-lregistering with:saidestqpsdevice avhemsaid member: is in:a:predetermined-angular position pan-1 interloclclplate; ofaarcuate. configuration sslidably :sepported on said high: cam: sector in-wthewicinity zofwsaid recess and displaceable valongkthe, peripheryiof said member ash-an: extensiomot-isaidshi'ghr cam sector; at leastmartiallyrto fill=1saaid.rsrecess permit registrationaof l-said .stoprdeviceand recesswonly [when rsaidsmember is rotated to said predeterminedpesitioniromaa ,particular direction ea =reversible-drivings system if-6'1? twsaid sel-ement and. .-said member; l sensing lmeansm' responsive to the orientation of :said member rel-ative 'totsaid predetermined,.;position, ier icontrolling Jahe directiontof rotationaoi .said system: toneitect direct homing of .said .member tow said predetermined position; and qyieldable .imea is iorgudisplacing said inter-lock plate position-ta eauseisaid sensing; means toceStabliSh 1:3, d-irection of. rotation-- epposite tosaidaparticular indirection l 9,-.-Apparatus --for positioning a rotary-vicaristrolled b-elementei-n a;preselectedvangularaposition loomprisingzmastop deviceior :controlling the-4:0- .sition 7 oflsaid element -a rotatable member having;:provisionsfbrr-registering +with saidwstopvdei-vice en1y-whensaid memb eriis in a'predetermined 5:30 angular;positionrand displaceable in onevdirection lover aasmallafraction; of;.a revolution; arreversitbledritiing, system forsaid,elementhandvsaidlmemulcer p sensin g-z means, responsive:- tottheorientation of sa "members-relative .to,said. predetermined positions for controlling {the directioniof, rotation [of :-'sa-id system to -a-e1fect--. direct homing :ofasaid ..member sto said predetermined position; and means for r displacing .sai-d -mem-ber twhenasaid (member his initially in :said ,-.predetermined Tposit;. ,-,tionsto causeisaid sensing-meanslto establishean opposite direction of: rotation.

110. iA1epar-atus .vfor wpositio-ningea rotary vroentro-lledielement in. a; :preselectedaangmzlar-iposition comprising: .411, stopdevice iorscontrolling i-the I .ei-tionsoi-l saidaelement; 5a-rotatable member-having provisions l-fora registering swithvsaid -stop;denovice :O'IIlY WhQIl said member --is .i-n 'a'ipredeteranined vangnlar position; means comprising Nat -least: amortioniofssaid memberzand displaceable 50 to:simulairerotation.- ofwsaid memberin oneldiree- 4 tion' over -a small inaction-10f;@asrevolution; ta rewersible 'drivi-ngrsystem ior said element and (-said remember; smeansHerr-energizing: said drivingssysatem rsensi-ngrmeans; responsive :toatheorientation ef isaid .member relative 'to said predetermined .position; for-controlling 'thB?diI-e(3ti'On-0f irotation aof .ssaid stem to eflect direct s-homingaof ssaid member to said predetermined wpesition; means -:for displacing -said-zdisplaceable means -,prioratoathe- :energizationof i said --driv-ing:-.system -Whenssaidr member is zinitially in said'predetermined position:to1.-cause said sensing means to establish win-voppositeldirection of a rotation.

. "v-. l.1. Apparatus wfor positioning :Ta rotary neon- ;etrolledielement inra preselected angular position 'ecomprising .=a= normally stationary member: displaceabie in one-direction overa-smalhfraction (of a-zrevoluti-on; -=-a =stop. device: for. controllingmthe y posi-tion q of said element; ea rotatable -member iplaeementxtherewith and also rotatablerrelative oto said staticnary-member said rotatable memrhaving provisions 2 for registering iwith.v said -.-.stopi -.device only 1 when said rotatableamemberais --havir 1g :hieh "fiend 1ow roam-ssectors eindir duallymmin aspre te m m n p i ion;.,-arreversible driving system for said element and said rotatable member; sensing means, responsive to the orientation of said rotatable member relative to said predetermined position, for controlling the direction of rotation of said system to effect direct homing of said rotatable member to said predetermined position; and means for displacing said stationary member when said rotatable member is initially in said predetermined position to cause said sensing means to establish an opposite direction of rotation.

12. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a normally stationary member displaceable in one direction over a small fraction of a revolution; a stop device for controlling the "position of said element; a rotatable member connected with said stationary member for displacement therewith and also rotatable relative to said stationary member, said rotatable member having provisions for registering with said stop device only when said rotatable member is in a predetermined angular position; a reversible driving system for said element and said rotatable member; sensing means, responsive to the orientation of said rotatable member relative to said predetermined position, for controlling the direction of rotation of said system to effect direct homing of said rotatable member to said predetermined position; and yieldable means for normally displacing said stationary member to cause said sensing means to establish an opposite 1 direction of rotation when said rotatable member is'initially in said predetermined position.

13. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a normally stationary member displaceable in one direction over a small fraction of a revolution; a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when said rotatable member is in 2 predetermined angular position; means for con\ necting said rotatable member to said stationary member for displacement therewith and for permitting rotation of said rotatable member relative to said stationary member; a reversible driving system for said element and said rotatable member; sensing means, responsive to the orientation of said rotatable member relative to said "predetermined position, for controlling the direction of rotation of said system to efiect direct homing of said rotatable member to said predetermined position; and means for displacing said stationary member when said rotatable member is initially in said predetermined position to cause said sensing means to establish an opposite direction of rotation.

14. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when said member is in a predetermined angular position; a planetary gear train including a rotatable gear of a given number of teeth connected to said member, a stationary gear of a different number of teeth, and at least one pinion gear meshing with said rotatable and stationary gears; a reversible driving system for driving said element and said member through I said gear train; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to effect direct homing of said member-to said predetermined position; and yieldable means for normally displacing said rotatable gear in one'direction over -a small fraction of a revolution to cause said sensing means to establish an opposite direction of rotation when said member is initially in said predetermined position.

15. Apparatus for positioning a rotary controlled element'in a preselected angular position comprising: a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when saidmember is in a predetermined angular position; a planetary gear train including a rotatable gear of a given number of teeth connected to said member, a stationary gear of a difierent number of teeth, and concurrently driven pinion gears meshing with said rotatable and stationary gears; a reversible driving system 'for driving said element and said member through said gear train; sensing means, responsive to the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to efiect direct homing of said member to said predetermined position; and spring loading means connected with at least one of said pinion gears for normally displacing said rotatable gear in one direction over a small fraction of a revolution to cause said sensing means to establish an opposite direction of rotation when said member is initially in said predetermined position.

16. Apparatus for positioning a rotary controlled element in a preselected angular position comprising:' a stop device for controlling the position of said element; a rotatable member having provisions for registering with said stop device only when said member is in a predetermined angular position; a planetary gear train including a rotatable gear of a given number of teeth connected to said member, a stationary gear of a different number of teeth, and concurrently driven pinion gears meshing with said rotatable and stationary gears and rotatable relative to one an other over a small fraction of a revolution; a reversible driving system for driving said element and said member through said gear train; sensing means, responsive to' the orientation of said member relative to said predetermined position, for controlling the direction of rotation of said system to efiect direct homing of said member to said predetermined position; and a spring interconnecting said pinion gears for normally effecting relative rotation therebetween to displace said rotatable gear in one direction over a small fraction of a revolution to cause said sensing means to establish an opposite direction of rotation when said member is initially in said prede termined position. v

17. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a fast rotatable member rotatable within a multi-revolution range and including stop provisions; a stop device movable from an inactive position into registration with said stop provisions to arrest said fast member in a preselected angular position related to said predeproviding a driving connection from one of said members to said rotary controlled element; a reversible driving system for simultaneously driving said members at a, preselected speed ratio; sensing means, responsive to the orientation of said slow member relative to said predetermined position thereof, for controlling the direction of rotation of said system to eifect direct homing of said slow member to said predetermined position; and means for displacing said displaceable means when said slow member is initially in said predetermined position to cause said sensing means to establish an opposite direction of rotation. l

18. Apparatus for positioning a rotary controlled element in a preselected angular position comprising: a fast rotatable member rotatable within a, multi-revolution range and including stop provisions; a stop device movable from an inactive position into registration with said stop provisions to arrest said fast member in a preselected angular position related to said predetermined position; a slow rotatable member controlling said stop device to permit registration with said stop provisions only when said slow member is in a predetermined angular position and having at least a portion which is displace- 18 able to simulate rotation of said slow member in one direction over a small fraction of a revolution; means for providing a driving connection from one of said members to said rotary controlled element; a reversible driving system for simultaneously driving said members at a preselected speed ratio; sensing means, responsive to the orientation of said slow member relative to said predetermined position thereof, for controlling the direction of rotation of said system to efiect direct homing of said slow member to said predetermined position and for establishing rotation in said one direction upon the homing of said'slow member; and means for displacing said portion of said slow member when said slow member is initially in said predetermined posi- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date May Dec. 25, 1945 Number 

